Solid tyre is the way to go similar to this
https://uk.rs-online.com/web/p/troll...B&gclsrc=aw.ds
Best cash I have ever spent, has the same consistancy of an inflatable but never goes flat, mine even has a couple of nails haning out of it.
Mine came from B&Q but loads of places sell them and with a bit of shopping about should cost little more than a kneumatic tyre and tube