Yeah the OTC 3633 and OTC 3636 are both incandescent and use the same bulb type the red filmed incandescent bulb "OTC3633-10" is like $16 for a 10 pack on Amazon.
I love the 3633 it's crazy good quality. If you want a lower grade quality version you can get the OEMTools mini coiled circuit...
I'm very late to the party but I am a firm believer that PP isn't really needed, for me it's harder to get out and on 98% of circuit problems I can find the problem using a incandescent test light.
I always prefer incandescent over LED circuit testers because they actually put a 150-250mA load...
I generally find LED based test lights useless for 90% of diag on automotive electrical diagnostics.
They usually use between 5-35mA of current draw which is nowhere near enough to stress a circuit to see numerous types of issues that normally occurs in a circuit.
A conventional test light...