Is there such a thing as a truly bolt on front disk brake and if so where can I find it ?
Perhaps - but as it'd hafta be a "clamp on" arrangement, I don't think I'd be able to trust it fully with the loads a front brake experiences...
...but there's some options available, the tricky/costly bits is the 29" size & if you're lacking a front disc hub as well, then you're looking at a hub, wheel build and front fork - add in the cost of disc & caliper... and suddenly you might want to consider just getting this & stripping it for parts & spares lol;
Genesis 29" Men's Mountain Bike
If you've the wheel, I'd check the local bike shops first, they very often have "take offs" - new or very slightly used front forks (& other components ofc) that the customer immediately upgraded from when they bought a new bike, then left at the shop 'cause they didn't want them or care. These parts can usually be had for pennies on the dollar, the shop more than happy to be rid of them. As 29" bikes aren't particularly common, this might be a challenge however.
Not to say it's impossible otherwise, disc hubs can be inexpensive and you can make caliper mounts yourself. This is steel & the rear wheel, but the concept is the same as any caliper mount (welding aluminum shocks can be tricky, best to disassemble & clean before applying heat);