There were rules for a marine in Necro many moons ago. However, I would say it might be better to do something else because terminators are big models.

1. Use someone elses models if you can for a couple of weeks. You never know, a friend may have some they wouldnt mind you using that they have stored away somewhere.
2. Look for pics online and print them out, stick to card or whatever and then onto bases. I used to do it years ago with Epic, 40k and WFB for units and models I wanted to try out/ Nice and simple and you can see what they are armed with without much fuss