I have always wanted to get a basket for my bicycle, since my first post on installing a rack. I finally found myself a suitable and most importantly economical solution. I want to do my marketing and put all my misc stuff in it, instead of using a backpack.
Photo: the basket was unintentionally put closer to camera so it looks bigger... it is actually smaller than the rack
Photo: side view for better intepretation of the basket size vs rack size
You need to take note of the opening of the basket to make sure that your velcro tape has the correct width to "pass through" the openings. I asked my mum to sew velcro tape into correct sizes for me. I am using 4 inch "hook" side and 13 inch "stick" side with 1 inch overlap. The total length of the velcro tape would be 16 inch. The velcro in the photo here are temporary velcro which I made using stapler for me estimate the length required. I recommend using at least two velcro tapes to secure the basket onto the rack. Place the velcro at the position on the rack where there are vertical bar on the rack to avoid movement on the longitudinal direction (see the cross in the photo above).
Add-on: If you have more things that is "bigger" than your basket, you would want to buy a elastic mesh net to cover the basket. I was told that the mesh net could be obtained from Daiso. I will pay a visit to Daiso to see if they have these items. I intend to get all of these so that I can use my bicycle for all scenarios. Mesh net to cover the basket, "single" hook to hold boxes, "triple" hook to hold bags.
Photo: mesh net, "single" hook, "triple" hook from taobao
It is useful as you can put "anything" in plastic bags in it, instead of using a backpack which would be uncomfortable. These basket are extremely useful for quick grocery errand (buying bread / milk). Hanging plastic bag on the handle bar is also uncomfortable and not safe (I'm sure you know it).
Photo: hanging plastic bag at handle bar - not safe
Photo: Securing a box on the rack using nylon string (for one time use only)
My bicycle weighs 14.9kg with the bicycle itself, light with battery, rear rack, basket and lock. The rear rack itself is 1kg+, torchlight + battery about 0.5kg, and the lock is also 1kg+. My bicycle nett weight is about 12kg+. Weight is not a main concern for me because I am not taking it for race / speed (my "engine" is not fast enough either... so I can accept my "hardware" (bicycle) to be heavy. Having a heavy bicycle also give me an excuse for not riding fast enough, ha ha ha.