1. I used MS medium from Sigma Aldrich and Phytotechnology Laboratories. Both are working fine. Some smaller companies such as Phytotechnology sell same stuff as that from Sigma Aldrich, but with a cheaper tag and equally good quality. So, you don't have to buy anything from a big-name chemical company.

2. Bear in mind that the most important thing to know is that there are different forms of MS medium sold by a company. You need to know which one you need. For example, there are such as: 1. MS medium w/o vitamin, 2. MS medium with MS vitamins, 3. MS medium with B5 vitamins, 4. MS salt only, 5. MS macronutrient-based solution, 6. MS micronutrient-based solution, 7. some even have sucrose added in .....it is confusion. So, you need to check carefully what ingredients the product contains before you place an order.

I have used MS media from Sigma Aldrich and its works good. You should have to purchase MS salt only. Some time we have need to media alteration for better result. 

Always Prefer Sigma Aldrich