Advice sought for options: HP 41 C/CV/CX Battery Pack

[mobi323]

I have a HP41 CX that is missing a battery pack.
I have searched Ebay and I find that there are only a few rechargeable packs available all of which require refurbishment.
I seem to have a couple of options:-
1. I can try to purchase an ordinary battery pack - the one that takes the N size non-rechargeable batteries. However they seem to be as rare as hen's teeth.
2. I could purchase a rechargeable pack and remove the charging circuit board and old batteries and replace all the internals with four non-rechargeable batteries. This would require fitting springs. (What size batteries would fit)?
3. I could refurbish the pack with new rechargeable batteries as described in keesvandersanden's excellent site, or,
4. I could purchase a refurbished pack. But these are mainly in the US and are more expensive that a whole used HP 41 calculator. Especially when one takes into account the prohibitive Global Packaging Service or the USPS.

I seek everybody's advice as to which is the best way to go.