First, you'll get little more on water than what you have on air. It's just a low end 450, not a 480 that shines with WC>
Second, if you can't find a Full cover WC block for your card, it isn't made. The block manufactures stick where the profit is. Few will even venture to make blocks for low end cards, and ones that aren't probably reference design.
Third, it will cost you $100 or so in TOTAL to watercool JUST the card, add another $140 for the rest of the WC.
Seriously, you need to be serious about what you want to do.
Buy the cheapest car you can, and put a supercharger on it. Same thing...............