The cheapest meltas i've found are the ones from GW direct. It's like 5 for £5.10 so you could get your marines and the meltas for each of them.
Or you could look at the Black Templar conversion kit which comes with 2. How many do you need exactly? because most bits sites sell them for £1.50 no really making them worth it.
"Ambition is the biggest killer of Momentum"
Starting afresh with my Chaos Space Marines.
Project Log Link (Placeholder) -
Project Rebuild, Reboot, Recycle:
Stripping, rebuilding and remaking my Guard army.