You can get a capillary tube type or one with an electrical sending unit at most auto parts stores. However if you panel mount the gauge the needles can be very "bouncy". A slightly more expensive Murphy Switchgage is very panel mount friendly and will give you accurate oil temps.
20w50 motorcycle racing oil with zinc has been proven to run cooler than conventional 10w30 in air cooled small engines. If you want to invest some research into it look at small engine/lawn mower forums with input from guys that run multiple mowers daily as a starting point.
After switching over and not letting your motor cool down at an idle (which I feel is a terrible idea), I straight shut it off in 30 seconds from full throttle. You will get more life and less oil leaks from that motor IMO, but take it for what it is worth on your own accord.