About a month ago I checked on a WMS 4XX machine 25 cent coin entry head at Rudy's and Nicole emailed me back that even though it wasn't listed on the website they had one. I ended up getting one from another NLG member while getting some other parts from him so Rudy's may still have it. They do have a 5 cent coin head listed at this time for $8.99 so that will give you an idea on their price for a 25 cent one. You'd need to call or email them to see if they still had it.
I've had guys tell me they've filed the sides of a 5 cent coin head and made it wide enough for a quarter to pass thru. But depending on how careful you are that could leave some scratch marks on the visible area.