There's no real "cheap" option to Latex. Latex is the low man on the totem pole when it comes to self skinning makeup. Vaseline is actually more expensive, causes shine, and it doesn't dry in the amount of time you could use it.
Raw Beauty above is right, silicone and gelatin are the only real alternatives but they both have their drawbacks. There's also Cabo-patch, which is very expensive.
For allergy issues, you might try a simple two part silicone like SkinTite from Smooth-On. It dries clear, which is really nice and it can be tinted with silicone pigments that give it an amazing translucent quality. The downside to silicone is that it is much more expensive than latex.
The cheapest alternative to latex is gelatin. If you are interested, I will get you the recipe. You just take your standard grocery store Knox baker's gelatin and it can be prepared so that you can melt it in 8 seconds in a microwave into a semi liquid form that can be applied to the skin and even shaped like silicone using a makeup spatula. I even use gelatin heads to practice my application and hair punching techniques. The big thing is it is messy and it only goes on hot which can burn if you aren't careful.
Lastly, you could mix up some cabo-patch which is super strong and dries clear as well and doesn't have the mixing problems that silicone can run into. That being said, it is the most expensive alternative by far. You just mix pros-aide liquid adhesive with cabosil, which is a flocked silica that is used as a thickening agent in most cosmetics. Be careful though, work outside and wear a dust mask, cabosil is extremely dangerous if breathed in dry. It becomes inert once mixed with a liquid. You can buy it by the tub from most makeup supply companies that carry pros-aide.
Hope this helps.