We have a blue Isla bike to sell. My 7 year old daughter who is tall has just grown out of it.
Isla bikes are the most lightweight you can get.
Let me talk to my husband about cost and size and get back to you
We have two Islabikes - blue and pink/purple - both Beinn 20's for age 5 plus. They are £389 plus delivery on the website. They probably go for c £300 secondhand as hold their value well. We would sell one of them. Let us know if that is what you are after.
I have a red Islabike Beinn 20 small - they do 2 frame sizes, the wheels are the same size. Our son was quite small for his age so we got this for his 6th birthday - its very lightweight - and would suit a 5+ year old. Ideally we would like £275 for it.