From OpticsHQ, you could get any E series light -- for $100 or less. Actually, you could get any incandescent 2-cell Surefire, or a 9P.
I'd recommend the E2e or a C2. The 6P isn't such a bad choice either, but it is possibly too similar to the Strion, except it's not rechargeable.
If you get an E2e, later you can convert it into an E2L or L4 with a KL1 or KL4 head, respectively. The C2 could be turned into an L5 with a KL5 head.