Based on this product's specifications, here are some alternatives and similar models
Lens cap Tamron CFA012 for Tamron A012 digital camera lenses, black
Summary description:
Tamron CFA012 lens cap designed for digital camera lenses compatible with Tamron A012 series. Finished in black, this protective cap fits to shield the front element from dust, scratches and light when the lens is not in use. Lightweight and easy to attach and remove, it preserves lens condition during storage and transport.