If you have a table saw or a band saw, you can make your own quite easily. For 0-27 sized rail, I've used luan (lauan) panels and for 0-sized rail, I've used 1/4" thick plywood. Cut a strip as wide as your tie length - I think it was around 2-1/2". Then, slice the strip into the individual ties - around 5/8" or so. The messy part comes when you dunk the things into the stain bucket, retrieve them, and lay them out to dry on old newspapers. Longer switch ties are quite easy using the same process.
Ther are vendors on Ebay that sell black and brown ties for traditional tubular track, and they are inexpensive. I would be more specific, bit it has been a few months and I no longer remember but they are readily available. I use traditional O gauge black tie tubular and I really like the look with the additional ties.
If you have O gauge tubular track and want to match those ties, the easiest way to make your own is to go to your local home improvement store and get the lath strips meant for fastening bug screens to doors & windows. It is almost exactly the same width and height as Lionel ties, and the top edges are slightly rounded like the Lionel ties. Cut it to length and spray it satin black.