The curved (bolo tines) are available for the FRC800. You need to look at the attaching points. You could use any bolo that matches the attaching points. Sounds like your tines are simply worn out. At least the only time I have seen knife like tines, that was the case. Bolos don't last too long in gravelly soils.

I suggest that you remove the tine assembly from either side and take it to your local Honda Outdoor Power Equipment dealer's parts counter. The parts person can quickly look up the tine types that were available for your model and then identify what you have. I don't know of an alternate source of supply for Honda tines.

Look at this way. You bought a great tiller for a great price and the only thing separating you from gardening happiness is the price of a new set of tines. Yes, they won't be cheap but neither was that Honda tiller when new. If you have reasonable soil and are not in business to grow things, then a new set of tines will likely last you 20 years or more.

Try the link below.

Here is a link that might be useful: Plano Power FR800 parts

You might also try:
http://www.milfordpower.com