If you are in the UK try
www.Ebuyer.com. They sell RockChip players (It's where I bought mine from) that would meet most of your needs:-
I'm looking for a player with the following features:
Stable firmware/operation (want it to last for years, why not?)
4gb, really 4gb (4096MB before format)
Long lasting battery
SD (or other type) memory expansion card slot
2 inch + screen would be big bonus
Only problem is the battery life only 6 hours max for RockChip