You can find them in tourist shops and in the russian market in Phnom Penh.
The real thing, as in the official shirt, I have no idea. Given the quality of soccer in Cambodia you could try to make it into the national team. That might be easier than trying to contact the federation and finding the official T-shirt-maker. And I only mean that half jokingly.
There isn't such a thing as a national kit. The soccer side hardly gets games and when they are very infrequent. As a consequence they get new kits every time they play a game or participate in the tournament. The kits on offer in Phnom Penh are just shirts with a Cambodia flag on them.
Andy's Kingdom of Football has the latest.
#3 uitcambo has been a member since 16/2/2011. Posts: 1
Thanks! And where could I find these shirts in PP?
#4 molocono has been a member since 6/9/2010. Posts: 24