If you like the idea of PC ties, they can easily be blended with bridge ties. Most of the PC ties I've found are 1/16 inch wide, which matches 10 inch bridge ties. The extra height can be added with wood or styrene strips. I've done it several tmes.
For a track gauge, if you're sure you'll never need it for more than a few bridges, a block of wood works fine. I made several from 1/4 by 1/2 basswood. Find a piece of properly gauged track and rub the narrow side of the wood on the rails to mark it. Then carefully file slots where the marks are. You'll end up with a track gauge good for at least several feet of track, and with care, it will last a lot longer. It also has the advantage that one can solder rails, while holding them down with your fingers, without either melting the gauge or burning the fingers. If the gauge does overheat and scorch, just make a new one.
I agree that the ME gauges are better, but for a one-use gauge, wood is fine. I made quite a few when laying my narrow gauge simply because commercial ones were hard to find. RLW had them, in resin, but that doesn't always work well with soldering, and with enough wooden gauges I could lay a length of rail without having to stop and reposition everything.
