www.dohavets.com

The have a good stock of stuff.

Also there's the pet supply shop in the old souq. If you're in the big open car park, walk down the road that goes past the left hand side of the souq, past the roundabout where the traffic warden in old style uniform sometimes is, and the pet shop is on the corner of one of the alleys on the right hand side. You'll see it as you walk past.