RTV 400ci - tires?

If I am repeating a thread, please excuse me, but I searched and couldn't find an answer to my question - so here it is:
I just purchased a 2012 RTV 400ci and need to replace the tires. It came with 24x9-12 and 24x11x12. I would like to get the HDWS type tire since it will be used only on firm dirt roads. I haven't been able to find a source for these in the 24 inch size. It appears to me that going to the 25 inch sizes can be done, but I don't want to spend $400 - $500 on tires that won't work. Anyone here have experience with this? Any advice for vendors would be appreciated as well.

Right after I posted this I found a relatively good deal on eBay for a set of front and rear tires in the worksite style for $524 including 4- day shipping. I am all set.

Hey biff I'm curious about the top speed of the 400? My x1100 is a turd at 25mph down hill with a tail wind... I knew this going in... actually I figured it would just rip up to 25 and govern out but it doesn't if I see 25 I feel like I'm winning the Coca Cola 600.

As I just purchased this machine, I have not really had it out for more than a test drive. It had a lot of deferred maintenance so I have been doing major maintenance on it. Besides it has been cold and snowy here so working on it in my shop is better than taking it out for drives. I have a X900 with a Boss V plow that I use daily - especially with over a mile of driveway in the woods. My X900 does something like 24 MPH, but I don't have any areas where I want to do more then 18. It is the power that I wanted and it is a bulldozer! The 400ci is for my summer work crew to use. Speed is not something I want for them.