i have a faulty electronic ignition on my stoves oven?

The fans revolve but the electronic ignition does not kick in. The only oven that will work is the top oven but i have to slam the bottom oven door to do so which can be several times to get it to ignite.The grill will also not self ignite. I have contacted stoves but they said the part is obselete!
What can i do?
Stoves double rotostar oven and grill - about 10 years old