There's no really practical alternative to using the space bar (other than using a different keyboard, of course). On a keyboard with a numeric keypad, it's possible to generate a space by holding down the Alt key, typing 32 and then releasing the Alt key. However that's impractical if you're tying more than a few words.
If you're using a desktop computer, a replacement wired keyboard needn't cost you more than a few quid. e.g. £8 in Asda:
https://groceries.asda.com/product/computing-accessories/onn-wired-keyboard/1000033144354
You can also use the same type of keyboard with a laptop, just by plugging it into a USB port.
Replacement keyboards for laptops generally only cost around £15 (although prices vary greatly, depending on the make and model of the laptop), with the instructions for fitting them often available on YouTube. (I've replaced several laptop keyboards myself. With some laptops it only takes a couple of minutes but with others it can be a more fiddly task, taking a bit longer). If you need the services of a technician though, DON'T go to Currys/PC World, as they'll charge you £60 (plus the cost of the keyboard) for just a few minutes work. Phone around local independent computer repair shops for a more reasonable price.