All you need is a set of original X/Y coordinates and some idea of what type of a grade you want to simulate along with a little trigonometry. Start with Hx, Hy, Sx and Sy, plug these into the attached calculator, and set your bike up to match the outputs. While not as elegant a solution as doing this on one of the newer fit bikes, you can achieve 95% of the same result just doing this. The only thing that this solution doesn't offer is the ability to tilt the bars and saddle to match the incline. I think most fitters will really just be interested in tilting the bike to simulate out of the saddle climbing with regards to knee clearance, so this should be easy enough to do here with good results towards the end of your fitting session.
Disclaimer - I haven't actually tested this just yet or checked my math so let me know if you notice any errors.
ACME Bicycle Co., Brooklyn, NY