Extension for selling bulk goods

Hi, I'm looking for an extension to sell bulk goods.

Example: Toothpicks in user specified length.

• The price should be dependend on the length and computed via a base price 10€/meter.
• The extension should be compatible with built in options like select and checkbox.
• A minium and maximum value for length should be configurable for each product.
• A minimum price should also be configurable like 5€. So that a super small toothpick wont be any cheaper than 5€.
• Ranges would be an optional awesome feature like 1-2meters has a different baseprice than 2-4m.

I found multiple extensions but all of them have problems like:

• Wrong inventory handling and product grouping.
• Adding a product of length 1m and product of 2m length results in product qty 2 length 3m in cart which is wrong they need to be two different entries in the cart like when using built in select option.
• Product dimensions are not respected or overwritten accordingly.
• Weight is not respected or overwritten accordingly.
• Stock management gets confusing since product will be cut on user request from a much longer bar.

Actually, if this shop use case is realizable it might very well be a new shop installation. So OpenCart 3.0 would be no problem aswell.

Is there any mature extension which can handle bulk goods like I described (paid or free)?
Thanks for your feedback!

Our Instant Option Price Calculator extension, perhaps in conjunction with the Number Option extension, might be able to do that.

BTW.: If the same product is entered twice into the shopping cart, with 2 different chosen option values, the cart will show them as separate products!

Actually I already took a look at your extension and I can say it was the best i was able to find for now.

However, one point I did not like that much was the need to override the price computation formular. Especially, that I have to consider built-in in options within that formular for the price to be computed right. I as programer can understand the formular grammer, but it overwhelms my assistants and it is pretty error-prone when options change.

It would have been really cool if it would behave more like a built-in select/checkbox option, where the price difference to the base price is computed and shown like (+ xx.xx €). For example, the user enters the length in the number field, and the difference price is shown besides the option field. Total price computation then can happen the traditional way like built-in options without overriding any computation formular.

I'm not familiar with programming opencart extensions specifically, but I'm fluent in PHP. Writing an extension myself may also be a viable solution if this use case can be realised in a reasonable timeframe.

Not sure if it is possible to add an additional custom option type with an extension though?

Using price formulas is optional, it's only needed for non-standard option price calculations. In either case, when choosing product options on the frontend product page, the product price shown is instantly updated via an Ajax call.