Way to only allow numeric in search dropdown for filament select element?

 Select::make('zip_code_id')
     ->searchable(fn)
     ->native(false)
     ->getSearchResultsUsing(fn ($livewire, string $search) => $livewire->agency->approved_zip_codes()
        ->where('zip_codes.code', 'like', "%{$search}%")
        ->limit(20)
        ->pluck('zip_codes.code', 'county_zip_code.zip_code_id')
        ->toArray()
     )
     ->required()
     ->label('Zip/Postal Code of the Request')
     ->validationAttribute('zip/postal code')
     ->reactive()
...