I'd imagine most compact cameras would withstand waht you are describing... Nothing really strange in what you write how you use the camera.
If horse riding and sitting on your belt does prove to be too hard for cameras like the Canon Powershot A530/540, then you should consider this camera:
Ricoh Caplio 500G wide.
It is very expensive ($600 or so?) but it is designed to withstand shocks, water upto 1 meter in depth. It is one tough cookie.
Canon EOS 350D, Tamron SP AF 90mm F/2.8 macro, Sigma 18-50mm F2.8 DC EX, Canon EF 70-200mm f/4 L USM, Tokina AT-X124 Pro 12-24mm F4, Soligor 1.7x C/D4 DG Teleconvertor, Manfrotto 724B tripod, Canon Powershot S30