Have you gotten any letters that give the reason for denial? It would be unusual if the only reason was lack of installment history. What you may want to do is go directly to the dealership and apply with them. If you have a provable income and a down payment they will certainly find a loan at better than 25% with your credit score. I would recommend a 10% - 20% down payment and a vehicle cost of no more than 50% of your annual income to start out and you should have no problem.
If there are other reasons listed for the denial you would need to let us know what they are and the members may be able to suggest workarounds for you.
Edit to add: Just saw your other post and the 2 months employment history is probably going to be a bigger barrier than the lack of installment loans. Lenders generally like to see at least 6 months of employment before they are willing to talk. You may be best off to lower what you are looking for to a reasonable used vehicle in the under 10K range.
Starting Score: 500's