On the question of sandbags (the kind that can be inserted into the lead block)

You can go to the professional fitness equipment to ask the place, you can also look online to see if there is, the kind of inserted lead

Tie legs

Now basically outdated, many people do not use that, now use are sandbags, a sandbag 5 kg or so,

Sporting goods stores

are sold, inserted lead that kind of bad to buy now!

Sports stores

are selling them.