Hi. 

You can buy donut ones plenty of places online, or shaped foam depending on where the most pain is, I'm just trying an air cushion made by repose supposed to help sore places, at nearly £70 not cheap but district nurse said a good idea.

Hope you can get something suitable, or others may reply with other ideas. 

Good luck. 

Billy 

Hi EmmaLou13

My sympathy to you and your dad

Since I was diagnosed with cancer, I have also had the problem as your Dad.

After a lot of searching I found a company which I bought an air cushion from. It's been such a success that I also bought an air mattress from them.

Try www.frontier-group.co.uk  

Their products can look expensive but, believe me, they are cheap compared to the pain I had and what your Dad is going through 

All the best for you and your dad

Chris