Turbulators are anything that creates turbulence in a flue in this case. Specifically heat exchange tubes. On high end boilers you will always find some type of device used to disturb smooth even flue gasses. Turbulent flow in the flue slows the gasses down from escaping the chamber while increasing the speed at which they flow in the heat exchange tubes. I know that sounds contradictory, but understand it like this. Rather than flow in a straight line, it swirls and mixes in the tube. The swirl travels a longer distance and give the hot gasses more time to transfer into the tube. Some research will give a lot more detail of what I can explain here.
Now what can you use for turbulators, well just about anything you can fashion to disturb a straight path. Some use water heater flue turbulators cut in half or cut down to fit. Some use chain or chains. Welded links on the horizontal tubes. Simple flat scrap metal cut to fit with notches and or bends. I would recommend everyone monitoring their flue temps, especially on a gasser. The hotter the temps means less efficiency or BTU captured from the burn. Also an early indicator of time to clean. Some see upto a 200 degree decrease in flue temps without increased creosote build up, sometimes reduced creosote and more fly ash instead. Close monitoring is a must to find the sweet spot or design that suits your stove. The infamous scotch marine tube design can really benefit from this. Found in the P&M, Empyre, Garn for example. Not all stoves will react the same, some might not like it at all. But if your seeing 500 plus degree stack temps your loosing a lot of energy and this might be worth a look. Is this for everyone NO!!!! But many have benefitted from turbulators, whether factory supplied or homemade.