Yeah fair enough,
I was gonna suggest getting a larger unit.
Any particular reason you heat your sparge water separate? Not telling you what to do, and I am by no means an expert but I bring the full volume to strike temp, then drain off my sparge volume.
I then let the sparge water sit while I mash, and just use as is. There have been studies done on cold water sparging etc, there is no need to have particularly warm sparge water but I have found I heat to about 70 and it's about 65 by the time I sparge.
Just a thought to save you $$$. you can but a 19L pot from Big W for like $20 if you don't have a pot. Otherwise, a 19L pot and one of those $10 camping stoves but that's just my opinon!
Regards