Basically beggars drop pots of gold and the easiest palce to hunt them is on the Farm area. There are 8 different pots of gold, they are completely identical, even the lore text is the same so using identify is useless (thanks devs for dropping the ball). Anyway to look at it you need to send a tell to the item link; since this is a bit confusing here is a screenshot of how to do it.
You need to make sure your item matches exactly the Could not find player text of the screen shot. You only need to look at the first 6 letters.
Anyway once you have the correct pot of gold give it to Seamus.