There are many of them. Some complex and sophisticated that plug directly into the Rx. TME is one and Dubro makes a simple system that is just a valve operated by a servo and requires tapping the crankcase on a two stroke. All systems require a separate oil tank as well as expensive 'snake oil' and tapping into the muffler.

Now the down side, gas engines are great smokers and glow engines are not. This is because of the much hotter exhaust temperatures of gas engines. Anything less than about .60 in glow is not going to be much of a smoker. Even then a Special muffler with a oil preheater is going to be required or a simple coil around the muffler or cylinder head should be used. Even for gas engines a preheater is a good plan.

John