eager load and empty queries

I'm trying to put my catalog in cache by team. Price may vary by team. But if the price is not set for a product I need to send the "default" team value", and can't find an easy way to do this.

$teams = Team::all();

foreach ($teams as $team) {

    $teamId = $team->id;

    $catalog = Cache::rememberForever('catalog-' . $team->id, function () use ($teamId) {

        $catalog = Category::with(['products.prices' => function ($q) use ($teamId) {
            $q->where("team_id", $teamId); // and if no result $q->where("team_id",1);
        }])->all();

        return $catalog;
    });
}

I was searching with queries like $q->whereNotExist, but I can't find a way to do it correctly. They may be some other way to do this via Product or Price model (and mutator), but I also stuck here.

Thank you.

via Chebli Mohamed