You could try your gym, although our gym doesn't sell anything at all and neither did our last one.
We use Gymnastics Express and Elite International. Both have been very reliable and helpful. Elite International are very helpful on the phone and will go check stock levels etc. Quite a lot of their clothing comes from the US or France, but they will order for you at no extra cost and obviously accessories are normally in stock and delivered straight away. Gymnastics Express I've only ever ordered from online, but always been very happy and delivery is very fast for both. Both good for straps, chalk, handguards, wrist bands, all the little gubbins.
Both the above sell Panda Paws. I think Gymnastics Planet sell Tiger Paws, but they're pretty much the same I believe and I've never tried Gymnastics Planet so can't recommend from experience.
Sports Direct sell chalk and are on most big High Streets or online, if it's an emergency chalk situation!
If it's actual equipment you want then Tracks 2000 or Continental.