The bolts in the knife shown are Corby Bolts, they are not the same as the things that Lion Steel use to assemble. Lion Steel just bolts together and the female part is a close fit in the tang hole, like a pin. The pictured conversion will be bonded together and ground to shape.
The screws that Lion Steel use are bespoke to them. If you are looking for bolt on scales that have been made to work with the original Lion Steel bolts, you will either need to get Lion Steel to send you replacement bolts, or you will need to find someone willing to make you custom fasteners, or you will need to find a way to modify the new scales to work with available off the shelf fasteners.
I bought a number of screws from
https://www.accu.co.uk/ but the female threaded rods I had to make on my lathe. McMaster Carr in the US sells threaded spacers, but a UK equivalent is very hard to find. I don't suppose you have callipers with which to measure the screws you have? Knowing what size outer diameter you need is a requirement for shopping for alternatives.