Judging by the movable control surfaces, I'd say it's either Airfix or Fr0g (spelled just like the amphibian, but this forum's nanny software replaces the correct word with "French."

) Yours sounds like it's more likely Fr0g, since it's molded in tan (I think the Airfix kit has only ever been molded in silver or gray.) If it is the Fr0g kit, then it's a B-25C (check the location of the upper turret..if it's behind the wing, then it's the Fr0g kit.)
Unfortunately, getting replacement parts will be difficult..the Fr0g kit dates from the 1960s and the original manufacturer long out of business. However most of Fr0g's molds ended up in Russia and the kits resurface from time to time under a variety of labels. It looks like the B-25 has been re-released in recent years by a Ukrainian company called "Eastern Express" (which has re-popped a number of old Fr0g kits.) A Google search shows several online vendors that have it for sale, so it may currently be in production. However, I don't know if the company has any service for providing parts.
Here's a link to a website showing the parts in the Eastern Express kit..you can check and see if it matches the kit you have:
http://www.hobby.dn.ua/product_info.php?products_id=59175&language=en As for accuracy, it looks like a typical 1960s Fr0g kit: very basic and devoid of detail. Understandable, as the kits were targeted mainly at kids.
SN