Sorry to hear this, sorry to hear you think people are being rude( in reality they are just trying to help, trust me)
I started like you, a beautiful black moor, in a 10 gallon, broke my heart to find this out almost a year ago too, but gave it away, sorry to hear this
I think the plastic tub idea is an excellent one, if you want those two to grow well an LFS be happy, I would get a 40 gallon tub, the general rule for goldfish is 20 gallons for the first one and 10 gallons for each one, I know that's 30 gallons, but I think they will be much happier in a 40 gallon
I know how you feel, I'm 15, and I get paid minimum wage, and with 20+ reptiles, that money goes by fast
Hey, you know what you can do with the 5 gallon, a betta tank!
I have a betta, shrimp, and an ADF in mine, it's great, you can do that with yours if you wish
Hope this helps