while it's possible that mentioning it to your employer may have negative consequences, I think it much more likely that your employer will get you what you need as far as an ergonomic workspace. Unfortunately you need to have some idea of what you need in an ergonomic workspace to ask. So if you have the money, try different things at home. You may also be able to borrow coworkers items to try them. Frequently, someone who has dealt with RSI and found some simple solutions will be excited to share whatever helped them.