If you are unable to find a Rescue near you who has a suitable Rabbit then if you go onto a Free ad Selling Site there are often Rabbits there ‘free to good home’. These Rabbits are unlikely to be neutered or vaccinated and of course you would not have any back up from a Rescue should the bonding not work out.
For bonding both Rabbits must be neutered. Age and size is not as important as the character of the Rabbit.
You will need a relatively small neutral area to introduce the two Rabbits. Putting the Buck into the bonding space first, waiting for a short while then adding the Doe. Don’t put anything in the bonding pen that either Rabbit can become possessive of.
It is usually better to keep the Rabbits together 24/7 rather than them having ‘dates’ and then being separated. So you would need to be able to dedicate ongoing supervision of the Rabbits for several days at least.
IME you will know very quickly if a bond will never work. I have probably been lucky as in the last 25 years caring for over 150 Rabbits I have only had one failed bond and that was a Trio.
As each bonding will have its own unique elements we will be able to give you more detailed advice once you start the process.
Good luck