Part of the problem is that Apple's patents and licence agreements on the MagSafe power interface have removed much choice in the market. There are very few manufacturers making DC-DC converter power supplies rated to replace a 65W or 85W MagSafe AC-DC power supply. If you had a Thinkpad with standard 19V input via barrel connector this would be much easier.
Briefly, whatever size of small solar panel you are probably bringing with you will not have the amperage to directly charge a Macbook/Macbook Pro/Macbook Air. If you want to charge an Apple laptop from a small solar setup you will want:
a) solar panel
b) small solar charge controller, MPPT type if possible
c) DC disconnect switch, you can use a $12 DIN mount type DC circuit breaker for this. You could glue it to the side of the battery.
d) 12V 10Ah size AGM lead acid battery. buy from eBay.
e) small 12V to 120VAC 150W true sinewave inverter. Should be around $150.
The general idea is that the solar panel charges the battery / keeps the battery full, then you draw from the battery (sometimes at the same time the solar panel is charging it, sometimes not) to charge the laptop.
With a Thinkpad or other laptop that has a non proprietary power interface you can use a DC-DC converter between the 12V battery and the laptop, something tuned to output 19V or whatever your laptop needs, and lose the inverter.
"Bicycling is a healthy and manly pursuit with much to recommend it, and, unlike other foolish crazes, it has not died out."
- The Daily Telegraph (1877)