Sleepyhead: depending where you live there should be a shop in your area that will seel vegan food. Normally in some kind of co-operative like 'Unicorn' or in generic 'health food' or vegetarian grocers'. You might find it easy to just bake a vegan cake, it really is very easy and cheaper than buying one. I would reccomend:
Moskowitz, I (2007) Vegan with a Vengeance: Over 150 Delicious, Cheap, Animal-free Recipes
Moskowitz, I & T, Hope (2008) Vegan Cupcakes Take Over The World: 75 Dairy-free Recipes for Cupcakes That Rule
Dieterly, L (2003) Sinfully Vegan: Over 140 Decadent Desserts to Satisfy Every Vegan's Sweet Tooth
Failing that, just do a websearch for a recipe - it will be easy to follow. The alternatives to milk and eggs are easy to get in any supermarket and cheap too.