I haven't ever seen any rebuild kits or even internal replacement parts other than maintenance items...screens & washer.
Can you take a photo of the broken part and post it? There might be some SS member that has a broken pump and might be willing to part with the item you need to effect a repair of your OEM pump.
Another thought, is to purchase one of the more economical Facet Gold Flo 24V pumps without "pass through feature" and use it to swap in place of the good Auxiliary transfer pump (first verify Aux pump is actually the same type as main pumps by looking at P/N on mtg flange) so you can use your original OEM Aux pump to replace the broken one.
Sometimes you can find decent Facet pricing deals at
Pegasus &
Aircraft Spruce. However, if purchasing the non-pass through type of pump it could not be used in tandem with your other primary pump and would be only for your Aux transfer. That is...unless you decided to just use a "single pump" to supply fuel to the injection pump circuit which is perfectly fine to only have one fuel pump w/o redundancy that you may never need. Offline redundancy could be provided by keeping a spare non flow through type pump on hand or just use the aux pump if you don't have it hooked up to aux fuel source.
Anyway, those are some options to consider.