Before you buy a /22 or smaller there are a couple of things you need to think about.
Are you an APNIC member already? If you are not an APNIC member yet, all you need to do register and pay the registration fee and you will be given a /22. You would need to become a member to receive any address space you need anyway so it turns out to be more cost effective just to register.
Are you getting the most space you can afford right now? IPv4 will only increase in value as the demand rises and the supply decreases, so the more you can afford and justify now the better.
The smaller the range the higher the price will be per IP. The smaller ranges are currently going for around $16-$19 per IP where as a larger range like a /16 will be around $10-$14 per IP.
If you have considered all of these and you know you need some IPv4 please Click Here to register your interest.