I think an auto parts store should have a handheld mechanical gauge that you could rent or buy. I'd try to hook one up to see if the oil pressure is actually low, or if the sender is just indicating low. The sender is based on resistance so it is possible that it could go bad (though I've not seen that happen before on this board.) Once you figure out if the oil pressure is actually low or only indicating low, you can go from there. I'd replace the sender before the gauge.
Former owner of a 1987 Supra Saltare. Current owner of a Malibu 23LSV.