I bought one of these tunnels recently:
http://www.petsathome.com/shop/large-small-pet-activity-tunnel-by-pets-at-play-15846
What i did was feed the ramp through the tunnel and tie it to the bottom and top cage bars so it doesn't move - i suppose you could also attach it to the ramp using velcro (i have seen iron on velcro strips in sainsburys).
I would definitely look in to re covering your ramp using an old piece of carpet. I did see a pic once of someone that covered their ramp using an old gym sock
![wink ;) ;)](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f609.png)
They just attached it by putting the sock over the ramp and using velcro at the top 'open end' (enabling them to remove it for washing)
There is also a site that makes specially designed ramp tunnels (cant think of the name off hand - will have a search for you)