In reply to Mad Mongoose:
You'll be simply wasting your time, money and effort trying to make your own.
It takes time, a pattern, a good sewing machine and skill to knock out trousers. They are one of the harder items to make at home. You'll; have to get any biase the right way and match too.
You don't need anything too fancy to climb in.
Over the years I' ve seen Ron Hill track suit bottoms come and go. Then there was a fashion for multi coloured baggy draw corded waist indian fabric style trousers. Plain old blue denim jeans were fashionable too. What next? Oh, yes, then there was a period where skin tight shiny material was used. Who knows what else was fashionable?
All you need is something that does not restrict your leg movement. Loose fitting work trousers should fit the bill.