The Dwarf Chain Loach (Yasuhikotakia sidthimunki) formally known as Botia Sidthimunki grows to 2.5" and occasionally comes up for sale in lfs, mine in Luton had a tank full not too long back, I wish I had bought some then. I'm pretty sure that I saw some at Maidenhead Aquatics in St Albans recently ... they were about £3.50.
Fish prices seem to vary enormously, I used to buy my Otos from my lfs at £3.50, they've now put them up to £4.50 but at MA in St Albans £1.50 and cheaper still if bought in 5's.