Gaffer tape will only take you so far.
But you can buy rigid rubber patches which you can put on the inside with some vulcanising solution - TipTop do them.
That works in perpetuity....
There is an atricle on youtube about first stitching (with a H/D leather needle and waxed natural linen thread) and then patch the back side up too and be as good as new. You might get away with just a large patch imo, tears grow but this may not as not that bad...