Just to make it clear, You don't want to use Axon-II, hence You ask for other available options. Right?
If You don't want to build Your own board - there are quite a few available out there, such as Arduino boards.
If You are willing to do soldering Yourself, then simply buy microcontroller of Your choice, some are cheaper than other, but normally they are not that expensive: from 50p for PIC to £4.00 for ATmega. If You don't mind programming in ASM, then PIC will be the cheapest option (some PICs are supported by C compilers). Nowadays there is a trend for AVR products, so You would probably be able to get more support from comunity.