I once walked around the complex wearing those dumbbells, 10 lbs in each hand. It took me half an hour and my limbs felt overstretched towards the end and I wondered if it is healthy do wear dumbbells for that long. I did some web searches and determined (and it seemed rational to me) that the safest way to add weight to walking is by wearing a weighted vest. So I bought this blue neoprene vest that weighs 12 lbs and I am loving it:

https://www.amazon.com/dp/B0040XF2RE

If I hold it in one hand, it feels heavy, but when the weight is distributed across the front and back, it does not feel heavy. I walked the same distance around the complex while wearing it and felt just fine. I am going to wear it for now and when I am used to this weight, I will upgrade to a 20 lb vest. I probably will still sometimes walk carrying dumbbells in my hands, but only for short distances.