Charge a Fixed Cost for Setup Fee for my Products

Hi,

Pls i'd like to know how i can charge a Flat Cost to some category of my products(e.g. Mould Fee or Setup Fee)
For example, i customize items e.g. Wristbands, Lapel pins, etc. for my customers which requires that they Pay a constant Fixed cost no matter the quantity they're ordering that will be used in making the Mould excluding the standard cost per product. I want the Fee to be added to their total bill in the checkout page.
I created an 'item' custom text field named "Mould fee"(read only) and restricted it to my Wristband & Lapel Pin category. which displays the Fixed cost of the mould in the product page.
How can i make this fixed cost to be displayed & added to their total cost in the Checkout page?

or Is there a better way to add this feature other than this method?
Expecting your reply. Thanks

Hi Nicholas,
Thanks

I've installed the plugin but i discovered that it adds the fee on all the products in my store.
How can i make it restricted to just the customized products categories because i sell other digital services which doesn't require this fee?
Thanks once again

Worked like charm.
Thanks a lot Nicholas