Spare rear wheel

I recently bought two used cromo bikes. They both have Shimano equipment and 7 speed rear cogs. The first one has STX cogs and hub (FH-MC32), the other Exage hub and 13-30 teeth cogs. My intention is to build rear spare wheel. I found unused Araya RM17 (32 holes) rim with spokes and nipples, and I have 7 speed cogs Shimano, that looks exactly like STX 11-28 teeth.
I am looking for best possible solution about the 7 speed rear hub.
Locals offer mostly 2012 or 2013 Shimano equipment, so I could buy a Shimano Acera FHRM70 for 17eur. For now that is the only 7spd hub I know. I wouldn't pay more than 30eur for a rear hub.
What hub should I consider?
It would also help if someone sent a shortcut to where this subject was already discussed.

I found another alternative: Shimano RM40 for 22eur. Is this a good alternative?

Hi and welcome to retrobike!

Put an advert in the wanted section below. - There will be plenty of STX rear hubs or similar available for low cost. Think the only thing that may make it a little harder would be shipping to where you are. What country are you in?

http://www.retrobike.co.uk/forum/viewforum.php?f=3

Or use an 8/9/10 speed hub and a spacer - an old 8 speed cassette spacer does fine, or you can buy purpose-built for around £3.

I live in Slovenia. Our post would send recomended 1/2kg package for about 6eur to Great Britain (so for about 5 pounds). I expect the same from your post...
I will go tomorrow to local store, where we usualy find some solution, however for now they offer only Shimano RM30 (has no water rubber protection) and some XT for 50euro, that seems a bit expensive to me for an old bike.
If I don't find solution tomorrow, I will write to 'wanted' section.

At the end I purchased a new Shimano Deore M590 hub. The seller also gave an alu spacer (3mm). It was the simplest solution.
Thanks for replies.