Is there a way to get a random gear from the catalog?

Unfortunately, I'm not aware of a direct way to do this. However, there are ways to do this by creating custom code to do so.

One way, although may be inefficient, would be to run a loop generating a random sequence of numbers and then checking to see if it's a valid asset, then checking to see if it's a valid gear item. You could even add a cooldown variable to the loop so if it runs a number of times, it can break the loop and stop any inefficiency going on there.

An example of something like this might be...

local market = game:GetService("MarketplaceService")

while wait() do
    local id = math.random(10000,999999) --Not sure what number range I should put in here
    local product_info = market:GetProductInfo(id) --Check to see if it's an item or not..
    if product_info then
        if product_info.AssetTypeId == 19 then --It's a gear item!
            print("Gear item found: "..product_info.Name)
        end
    end
end