I'd be surprised if you can find replacement GB hoods.
There are a few (mostly US) sources of NOS/repro hoods for Universal, CLB & Campag but they tend to be eyewateringly expensive ($40-80 a pair).
Do what you can to keep the ones you have - the only other option is the Cane Creek hoods on ebay (~£12) you may be able to tease into place they'll probably not look as good as the ones you've got.
I'd be surprised if you can find replacement GB hoods.
There are a few (mostly US) sources of NOS/repro hoods for Universal, CLB & Campag but they tend to be eyewateringly expensive ($40-80 a pair).
Do what you can to keep the ones you have - the only other option is the Cane Creek hoods on ebay (~£12) you may be able to tease into place they'll probably not look as good as the ones you've got.