Be careful man, you're asking to get yourself in trouble. I would not advise asking strangers. Do you have friends that smoke? Ask them. Maybe even hit up people you used to know.
Three days isn't too long to go without and if it's really that difficult for you you should consider taking a look at your smoking habits. It's really easy to develop a problem with cannabis (I have personal experience here).
If you're just looking to get high there are some options but I don't recommend messing with a lot of them. Kratom is probably the best option, it is not a straight up opiate at all but they are very similar in terms of effect. Kratom is much less habit forming with much less severe withdrawal symptoms and is much easier to stop using. However if you have an issue with substance abuse (I promise I am not judging mate, I have this issue personally) I wouldn't suggest going down that road.
Use something like benadryl to knock yourself out at night; if you're used to wake n baking or smoking during the day then this won't help you, but if smoking is a nightly routine for you and you can't get your hands on any then otc sleep aids can help you get through dry spells.
Another option is reclaim. Dry hit your pieces as hard as you can and then scrape them for resin. I know its not the tastiest but resin can bring sweet relief during dry spells. Tear your grinder apart and scrape it for keef. Another option is washing your grinder in isopropyl alcohol and then pouring the wash onto a baking sheet. That iso will evaporate out and leave you with some smokeable goods. And lastly (and the most desperate) you can search your floors and counter tops where you smoke and prepare to smoke for tiny nugs and crumbs you may have dropped.
In the future try to prepare for dry spells. Maybe use only one piece to get as much resin as you can, or invest in a kief box. Collect your stems. If you vape, save your AVB. If you don't vape, get a vape! By in bulk (qs or 1/2 os) and make it stretch.
I hope any of this was helpful to you! If you have any questions don't be shy.