You could get a spa panel that has extra room in it for a second breaker. Unprotected circuit breakers are much cheaper. https://www.homedepot.com/p/Midwest-Electric-Products-50-Amp-240-Volt-240-Watt-Non-Fuse-Metallic-Spa-Panel-Disconnect-with-GFI-UG412RMW250P/100686230