We have a hurdle and gate man who turns up on the doorstep about once a year, with a trailer load of his wares. We bought solid sided hurdles from him a few years back, as well as a sliding divider for separating out the sheep into two groups. The solid ones are very heavy but otherwise have done us well. The top part is open for the depth of one bar in normal hurdles and lambs can hop through this (they climb on their dams' backs) so we put ordinary hurdles round the outside when the lambs are young. Our main reason for using the solid sided hurdles is to prevent damage to the horns of multi-horned Hebs, as these are quite delicate in lambs.
Now I know you'll want to know how to contact this chap.....well, I haven't got a clue

, he just turns up. But I think if you were to google hurdle and gate fabricators you might be lucky. His family make all the gates etc and I think he's based somewhere like Lancashire.
Aha - Mr F has just said the contact details are on the hurdles, so when we go up there we'll check for you.