Is there a way to get reimbursed for ASU alterations and purchases?

In a word - No.

You can however count care and modification cost of your uniforms as a tax deductible expense (of course, it will only help if you itemize and pass the 2% threshold).

The Army does give you an annual uniform allowance, but it's a one time thing for reservists (unless called to active duty > 90 days).

You can claim uniform expenses including dry cleaning and alterations on your taxes. I do every year. Military Onesource is a useful tool to check out around tax time, you can also include mileage if your drill location is 100 miles away or more. Go over those options with whomever you do your taxes with or research it if you do them yourself.

Being in the National Guard, you should have a Supply Section with many of the items you need. For example, one of our troops just pinned SPC and she needed rank for her ASU. Supply handed it to her. Another guy needed his service stripes and Supply took care of it. Marksman badge, Supply.

You are supposed to get a one time issue per ribbon earned, Supply handles that. S1 just finished updating my service awards, once it hits iPerms I have to add 4 new ribbons to my rack. I'm going to Supply at the next opportunity to get them.

The downside is that your Supply Section might not be stocked so you have to request the item and wait. If this is a time sensitive issue I recommend hitting your local PX if one is available as the PX will usually be cheaper than purchasing items online.

When doing alterations, I recommend places near a military installation or on the installation. When I needed to have my rank and service stripes added I went to a dry cleaner/alterations place on my local Air Force Base. They also handled Army and Marine alterations thankfully. So you will also want to make calls and ask around to ensure the place handling your uniform knows what they're doing. I've seen plenty of horror stories from subpar alterations shops that have ruined the uniform and offered little or no recompense for it.

You can not get reimbursed, but you can ask your unit for all the awards and add-ons and then pay for it to be done. That would at least help with the cost of all of it. Also, depending where you live there may be places that will do the alterations for a much cheaper cost due to military. Where I live in OH we have an awesome option in Barberton called Star N Stripes that has done all my work over the years and they are very reasonable.