It's definately not a bolt on upgrade. Nor is it cheap. Beech's kit is over $4,600 and none in stock. Then you have to add the labor. Beech estimates 24 - 30 man hours. There may be others, but I would bet they aren't much, if any, cheaper.
I would look for ways to reduce amperage needs before I spent that much money. Overhauls on the 100 amp alternators are high if done by a reputable repair station. What you'll get today are Kelly Aerospace (Prestolite) alternators and I wouldn't have one if they gave it to me.
The first items I would change are the landing and taxi lights, and the NAV lights. There are LED replacements for all of them that will reduce their amperage requirements dramatically. Non-dimmable interior lights are also candidates for LED replacements.
HBC Kit Information:
ALTERNATOR, 100-AMP (24-VOLT)
A36 E-1111, E-1241 AND AFTER
A36TC EA-1 AND AFTER
F33A CE-748, CE-772 AND AFTER
F33C CJ-149 AND AFTER
V35B D-10097, D-10120 AND AFTER
THIS KIT PROVIDES PARTS AND INFORMATION TO INSTALL A 100-AMP, 24-VOLT ALTERNATOR.
WT. CHANGE :
F33A, F33C = WT: + 6.0 LBS @ 11.0 ARM; 66.0 MOMENT
A36, A36TC = WT: + 6.0 LBS @ 11.0 ARM; 66.0 MOMENT
V35B = WT: + 6.0 LBS @ 11.0 ARM; 66.0 MOMENT
EST. MAN/HRS: : 24 TO 30
MEN : 1 (MAN)