I would definitely recommend Omron. I've had mine for about 10 years and still functioning and accurate. You can get them on Lazada but beware any under P2k are likely to be copies or just Chinese junk. If it's sold under the LAZMALL banner it should be OK. It's useful to get one with the AC adaptor so you don't have to rely on batteries.

 

I'm not sure there is a "best brand". Inside these things they have a pressure sensor (basically a barometer) and a computer monitoring the pressure to determine the systolic and diastolic conditions. A barometer is a very simple device and I suggest they are all the same. I have a weather station which has a barometric pressure sensor and it agrees very closely with nearby weather station.

I had an OMRON brand blood pressure monitor and it pretty much agreed with my Dr's OMRON bp monitor. Some one gave me a LIFE BRAND bp monitor. It agreed pretty much with the OMRON. Note; I say pretty much because if you take blood pressure a couple of time in a row the reading will vary slightly.

Mercury carries the OMRON brand monitor. I would check the prices on Lazada as Mercury seem to be more expensive than other suppliers.