We currently run a Magento store and would like to charge customers an additional charge for Large/Bulky items.
I know we could simply set the price higher for these items in Magento, however this does not look very good from the customers point of view. They will see our price is higher than our competitors and move on. Ideally we would like to let the customers know there is an additional cost and give them a reason why.

I found a work around online where I can use Magento's 'Custom Options' to achieve this. (See images if you are curious).
However, as Linnworks does not work with 'Custom Options' we would have to manually add these Custom Options to a lot of products and would have to continue doing so every time we have a product such as this. This would become quite impractical.

Would anybody out there have any advice on how they have handled situations such as this?

Any advice would be much appreciated.

Thanks in advance.