Platypus bottle and an Aquamira Frontier Pro water filter together weigh only around 3 ounces. Rolled up together and ranger banded up, they make for a very compact package. Combined price is about $27 from Amazon.
Note that the Aquamira Pro is good for removing 99.9% of cryptosporidium and giardia and also improving water taste, but it won't do anything for smaller bacteria and viruses. Purification tablets kill bacteria and viruses within 30 minutes, but they need 4 hours to take care of the bigger bugs that the Aquamira Pro will remove. So, when using this setup with purification tablets, you can be drinking completely safe water within 30 minutes. Depending on the packaging, you can include the purification tablets in the rolled/ranger banded kit.
The clear Platypus bag can also be used for SODIS - set in sunlight for 6 hours and the nasties will be fried by UV rays.