I have found a 3 digit name that I like but all variations have been registered other than, .org .info and .biz.

I'm not interested in .uk domains at present, what would be the best option to buy???

Its very hard to get a 3 character domain name.

All 3 character .com domain names are gone. I think .co.uk and .net are also pretty much all taken give or take a few letter number combinations.

to help choose between .org .info and .biz try and think about what content you may have on the site....