Doing taxes for 2018, and trying to determine amount to claim for a motorized wheelchair donation.

My mother was diagnosed with ALS a few years ago, and as the disease progressed, her insurance paid for a motorized wheelchair. We received the wheelchair one week prior to her passing away, but she was never able to use it. I donated the wheelchair to the ALS Association not long after that, and received a letter serving as a tax receipt and thanking me for the donation. The letter stated that "only the person who donated the item may legally document the estimated worth of the donation".

The motorized wheelchair was brand new, and the only paperwork I was able to find after my mother's passing is a delivery ticket that has a list of charges for the wheelchair and accessories in an "Ext. Allow" and and "Ext. Charge" column. The total for the former column is $22,810.45, while the total for the latter is $35,840.00. My thought was that if I claimed the wheelchair as a donation, I would do so at the former value.

I am using a CPA to do my taxes, and he stated that he wasn't sure what to value the chair at (nor does he know who to contact concerning something like this). In his experience, donations that are more than $5,000 tend to attract the attention of the IRS, who might reject either value that we previously planned to claim and "could possibly stick me for a few hundred dollars in penalties" if the IRS rejects our justification for the amount we list.

I could just forego claiming it on my taxes and not worry about it, but my taxes are much higher this year because of income gained through monies I received as a result of my mother's passing (403b funds and pension), and the donation would make the difference between me getting something substantial back, or just a few hundred dollars (which would likely just go toward the cost of the CPA).

Can anybody who has been in a similar situation (as the client or the CPA) provide any insight into this?