I have a trolley which i purchased more than 15 years ago new.
Never seen them for sale since.
If any one is interested i can take some photos of it if they wish to make their own.
Not too difficult if you did a bit of metal work at school.

The only concern was under sharp/fast cornering it could tip over due to the high centre of gravity.
Would be simple to slightly redesign it to sit lower though.
WA66