I can think of several possibilities - I don't know what works best for you.
Contact RYCA and buy theirs.
Find the length you need and see if Fastenal, MSC, McMaster-Carr, Graingers or similar places have what you need.
Use metric or US threaded rod and use cap nuts on both ends.
Cut and re-thread your existing bolts (This usually doesn't work too well as the bolts have been hardened after the threads were rolled). It is tough to cut new threads as the diameter of the unthreaded portion is usually just a bit too big for the die, and the hardened metal is tough to cut cleanly with a die.
Cut your bolts in the middle and take out a section - then weld them back together in the middle and grind/machine the welds down. You would probably need to make a jig to help you weld them - I use a piece of angle iron and lay the rod in and tack weld them after grinding a taper on the ends to allow the weld to penetrate fully.
Search through the parts list of other bikes and find bolts of the proper length and diameter.
I looked at the Suzuki Parts list and the 2 front engine bolts that hold on the footpegs are 10x323. Fastenal offers bolts that are 10x300 and 10x280......not sure what length you need and what would work for you.
http://www.fastenal.com/web/products/detail.ex?sku=39191http://www.fastenal.com/web/products/detail.ex?sku=39192