If this is a frameless acrylic window it will be custom (buy new acrylic lens from a local plastics shop and seal it in place with Dow 795), otherwise if a framed fixed or opening portlight it will likely be a Lewmar and likely available. Do a search on this forum on "portlight replacement" and you will many threads on this subject. Replaced 4 portlights with used BoatLife Life Caulk to seal the frames last week.
Being able to fix boats allows most of us to enjoy this passion of sailing. Not everyone is cut out to be a DIY owner.
Windows are a 5 on the 10 scale of difficult tasks. Look inside to see if the outside issue caused inside damage to the wood and cushions. If no than the window is straight forward as @sail sfbay identifies.
You may be able to clean the current windows up and the properly reinstall. If the damage is more extensive then rebuilding the frame opening could be involved. You will not know till you get into the project.
An allowance in the cost of the boat is reasonable.