To get a super red big ear, your best bet would be to get a red big ear.
The fry will be reds/multies who are big-ear geno.
Breed the two reddest fry together.
Ideally, as you have both male and female reds. Get a male and female big ear.
Do two crosses(male red, female big ear. male big ear female red). Now you have two lines to work with/cross that are both bigear geno.
Pick the two reddest out of all the fry and spawn those.
You should start seeing more red/less other colors.
You can spawn another sibling back to one of the red parents and to get redder fry to cross with your now F2 reds-in-the-making big ears.
I saw a red dumbo super delta on ebay the other day, so just keep an eye out. If I see another I can pass the link to you...but I don't know where you live so I can't say if they can be shipped to you or not.
EDIT TO ADD: found a listing, can't promise quality or availability, but you can message the seller and see if that red is still available:
One of the cheapest big ears I've seen.