Welcome, SmallStripeslawncare. Sorry about the delay in getting in here.
You should have no problem finding a 19 inch mulch plug, but I prefer the cut of a LB without the mulcher. Seems as though an hour or so into mowing there is a buildup under the decks and the quality of cut appears to deteriorate, but that's just my personal preference.
Gas can. Better idea here. Run a very good quality synthetic oil and use the same mix in all your equipment. Amsoil, Lucas, Opti2, etc. Then run everything at 50:1. I am using Amsoil at the present time. Like it very well, but any synthetic oil that is a name brand and advertises protection up to 100:1 will work for you.