Otherwise I do not see any other option (other than perhaps sending Bitcoin between CEX accounts since crypto exchanges have a different internal system and on many exchanges it costs nothing to send Bitcoin to another account.
But trusting a third party with your money is not really the purpose of Bitcoin.
And since you said its on your Electrum wallet, I see no other choice than to pay the high fee.
The exchange option you’re suggesting would also not be a right idea, it can only work if the seller or buyer actually uses that same exchange with each other than the sender can do an internal transfer which doesn’t attract any fee. But if the recipient is not using that same exchange which is mostly common since merchants do not use exchanges to receive payment then on chain transaction is required which is mostly expensive on exchanges due to their fix charges.
1. Make weekend transactions often
Last weekend I tried to wait till Saturday midnight to see maybe there will be changes but there wasn’t, so I think this particular option is no longer viable again.
A good idea but it will just be best if he pays the shop in their legal tender direct except if they do not accept fiat payment which is rare, spending in fiat will be better than going in circle of buying this Altcoins