I have used bar or rail pickups on the two semi-hollow basses I have done. Both were routed for standard humbuckers. It was difficult finding something that would work and also fit in the rout. On the first I used full-sized lipstick tubes that fit in the "ears" of the humbucker rout without too much difficulty. These use bar magnets so spacing is not an issue. On the second I found a deal on some NOS Bill Lawrence EB-50 bass humbuckers. If you compare them to the guitar pickups the rail is much wider. I didn't really set out to use rail pickups, but they were the right size, the right price, and they sound great so they have been there ever since.

EB-50s were designed for bass although they look like the guitar L500 pickups. The specs are quite different though. To my ear they sound like a P-bass pickup with a bit more high end sparkle.

I have never used Toneriders, but others here have really liked them.