In the 2 years since my original post I bought one more of these souvenirs. Not expensive as you say, Alan. I presented the second one to the Shanklin Chine Heritage Centre.
The glass museum has made a collection of about 20 Isle of Wight souvenir paperweights, ranging in date from the late 19th to early 20th century. Shanklin Chine, Carisbrooke Castle and Ryde Esplanade are well represented, but there are some obscure ones, like one of Whippingham Church. These souvenirs are not that easy to find, but I have alerts set up on various auction sites.
Anton