Lots of GMs restrict what items can be bought in their campaigns. It helps if these same DMs put thought into what items Players would find useful and maybe discuss it with them between games.
Originally magic items were things you discovered or made after lengthy research and quests for materials. In 3rd edition (and by extension pathfinder) there are rules for crafting and buying items but these are very much guidelines.
Best thing is to check with the DM and discuss it among the group.
There is no hard rule governing this.
The Gamemastery Guide has some guidelines under the headline settlements which states that a settlement (a village, town, city) has a base value. This is a measurement of how expensive magic items can be commonly found in the settlement - in a large city you'd have a 75% chance of finding any magic item with a price up to 8000 gp. There would also be more expensive items, but only a few of those. These settlement guidelines does not make a difference between wondrous items and other types of magic items. All types of items would be available.
Your GM, however, has the final word in her own game. It is absolutely in her power to say that wondrous items can't be purchased. She should not do so lightly, however. The game assumes the party is well supplied with appropriate magic items, if these aren't supplied via treasure found then they must be purchased - otherwise game balance suffers.
It's easy to fall in the trap of restricting magic items. I know because I've done it. Fully equipped characters soon light up like magic Christmas trees. I and probably hordes of gamers find such commonality of magic items to be quite ridiculous. It takes away the fun of finding treasure and the mystic of magic if it's so darn ordinary. But that's the way Pathfinder is. Either get over it or use an alternate rules subsystem such as the automatic bonus progression to lower the amount of magic items.
Talk to your GM. Ask what you're supposed to spend your hard earned gold on if much-needed wondrous items are out of the question.