Any Suggestions?

Just got my 120k voucher. I want to make something which will help against magic users and especially beholders. I'm thinking bracers or belt preferably any suggestions???

Beholders. What fun...

Long story short:

Beholders have a few very nasty abilities that you will want to protect against- Petrification (you need a statuebreaker cloak for this, custom items wont help), Death Ray (death effect immunity used to not work against this, but it may be fixed now?), Slow (freedom does the trick here), Knockdown (you need earthrooted boots for this as custom items cannot protect you), and Confusion (mind effect immunity helps here). Dont bother trying to use temporary buffs from spells, including items, scrolls, or potions. Beholders automatically dispell these things as soon as they spot you. You need item properties to have a chance of being protected.

Once you are effectively protected from all that rubbish.... then you need to be able to avoid the damage the gas bags can deal... and its a LOT. You will either need a very high touch AC to dodge their rays, or you will need very high SR to resist them. There is nothing that can protect you from magical damage, so you must either not get hit or outright resist the magic.
A touch AC(does not rely on armor, natural armor, or shield bonuses) somewhere around 30 or better, or SR of 30+ will have a reasonable chance of protecting you. Even better if you have both

Otherwise, if you cannot manage all that, your best chance is to sneak into the room and use some form of Area Effect magic to incapacitate/disable the buggers all at once. Mind you, their will saves are not shabby... reflex and fort are your best weak spots to target.

I could give more detail here, but I dont want to take *all* the discovery out of it... suffice to say I died an AWFUL lot to learn what I know, and I am FULLY aware of how frustrating beholders can be.

My recommendation on what "slot" to use for your custom item really depends on the type of build you are going for. Gloves are usually a safe bet. Shields and armor can also work. The concern is to not use up a slot that will preclude you from making use of some of the rare items in game that have properties you cannot get on your custom items. For example, the boot slot is the only slot that you can get items to grant improved evasion or knockdown immunity (its also the only slot that can get you a Dodge AC bonus, heh, dilemmas, no?)

One last thing to watch out for.... while beholders themselves cheat like the dickens... the beholder Elder is ridiculous. You wont be sneaking up on him, so dont bother trying... and if you decide to engage him, you better kill him FAST... also, get yourself some Lysis Bracers

Dave pretty much nailed it on the head.

The only minor difference in my opinions would be the AC/SR, in that some good SR is required for decent survivability. With a full spawn, you're gonna be rolling enough numbers that the beholders will roll a 20 and hit you. SR provides an extra layer of "armor" against the rays; not only will they have to roll a 20 on the touch attack for the eye ray, but also a high roll on the SR check to beat your resistance. If your SR is high enough that they have to make a 20 on the SR check as well as the touch attack, your odds on getting hit by a nasty beam go from 1 in 20 with just the touch AC to 1 in 780 with the high SR

A side note too... For touch AC, natural armor bonuses are ignored, but that's the "Natural" armor type as with the amulets. Pale master, RDD, monk wisdom AC, and expertise/imp. expertise AC boosts are also considered "natural" armor, but of that "other" type of 'natural armor', and they do count towards your touch AC

As for the custom item itself, using a voucher to "upgrade" an existing item is also a possibility.

Thanks guys. How does an upgrade work? Do you get an extra 120k of stuff on top of an existing item???

You can upgrade an existing custom item.

You add the value of the new voucher to the value of the old voucher to determine the total value limit of the upgraded item.

Keep in mind that any modifications from other sources, such as elemental crystals, the mystic forge, the dwarf wizard, or the Maker etc, will be lost when you upgrade and you will have to add them again if you wish to get them back.