Bike Frame Battery Holder

I'm looking for custom battery holders to attach to a mountain and road bike frames. The holders should be made of plastic and is capable of supporting a small portable battery. The specific capacity isn't determined yet, so flexibility in design is key.

On the mountain bike, it would be mounting on the back side of the seat tube down close to the derailer. See bike image attached.

On the road bike, it would be mounting on the down tube below where the bottle cage attaches. See bike image attached.

I can provide dimensions & up-close pictures of the areas referenced.

Ideal Skills and Experience:
- Experience in designing and fabricating bike accessories
- Knowledge of battery holder requirements and safety
- Proficiency in working with plastic materials
- Ability to create adjustable or adaptable designs

Please provide samples of previous work and any relevant qualifications.