Welcome to Geekhack!
I use an SSK at work and one at home - very buckle
That's the TKL version of the Model M, btw.
If you scour eBay, you will find that they often appear, usually in reasonable condition.
Also look through the
classifieds as they do appear there from time to time.
Finally if you have any computer recyclers or charity shops in your area, you might call in from time to time to see if they have any really old keyboards that otherwise might get thrown out. Those ones often need a good cleaning, but fortunately most Model M keyboards clean up very well.