It's not difficult to remove the window frame from the RV and the glass can be replaced by most any glass shop IF they are willing to tackle a window they are probably unfamiliar with. There are glass companies that do "RV foggy window" repairs every day and could handle this easily, but I don't know who to suggest in your area. Some are Suncoast Designers in Florida, RV Fog Dr in Arkansas, Dave Root Glass, etc.
Removing the window from the RV is a reasonable DIY project, even if you've never done it before (their are YouTube videos on the process). If not willing to tackle that, figure around $200 to remove and re-install the window plus whatever the costs of the actual glass replacement. A real glass shop could do that for around $100 (dual pane glass) but those not in the daily RV glass business would probably contract out to a custom dual pane glass provider and that could easily be 2x or 3x that.
You could try RV salvage yards for a similar size glass assembly, but you still have to pay for remove/install if you cannot DIY. Click the RESOURCES button and select Parts suppliers to find a list of salvage yards. Or just Google 'rv salvage'.
