A leather artisan has custom make the casing for me. I told him what I like and gave him a free hand in doing the casing for me. If you are from Singapore, you can go to this shop at Heeren, 4th floor Annex Building. The name of the shop is 310 Woodland.
I only know of one other place that 'mass' produce casing for Hanlin v3 online - you can check this out at this online shop:
http://www.stylzworld.com/shop/beboo...319784f11dca85