We use bikes made by Giant. They are called 'Halfway' and are fine for us 'oldies'. They have 20 inch wheels so are big enough to ride properly and not look a total plonker on the baby wheels. Ours do not have geras, but the newere models do. They fold very easily and come with a storage bag so they can be carried in the car boot, or on the bed in the van.
Have a look at their web page if you like.
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