Indoor exercise bike

Contact your mutuelle or their website, very often they have exercise bikes and other equipment you can hire cheaper ,
else try second hand webistes and resell after usage.

I have a nearly new, perfect condition, modern indoor exercise bike for sale TINTORI C6, little used. Good price.
https://resources.t-fitness.com/bilder/tunturi/crosstrainer/c6_detail.jpg
Contact: email.odin@gmail.com
AUDERGHEM

If this is a genuine medical need rather than just something that you feel is a good idea, contact the hospital where the surgery was carried out and ask their advice. Or, as suggested by Emille, try your mutuelle.
It is quite possible that they will lend you one free of charge.