I don't have any pre-built recommendations, but you can figure out some dimensions and find someone online who'd be willing to 3D print it for you.

Or you could find a machinist. That'll be fairly expensive, though.

Lastly, you could probably make it using supplies from Home Depot, like PVC pipes + fittings and PVC cement, maybe some gasket sealer for any holes you drill. Probably the cheapest option of these 3.