i do not know if theres a source online, try a google search. I make my own but if you dont have the tools can be difficult, you dont need much though, online you can find plenty of instructions for the "backyard mokume gane maker"

if you dont have the basic metals some people did it stacking coins, like pennies and quarters they already have a core of other metals, but if you can stack other scraps its more than fine, keep them pressed in an homemade clamp and build a little "oven" with fire bricks, round, leaving an hole open in the bottom to let a torch in, this way placing your piece in the middle the heat works its way up in circles, the result is the same of a kiln, be careful not to melt the stack.
Laminate the stack flat and with a saw and a drill, or better some jeweller bits, carve some random shapes, holes etc, dont go through or send the drill bit down, keep a conic hole, and better avoid going out the edges, keep laminating and working the stack until reached the desired result