Just as a matter of interest, there is a really nice free calculator designed by a Thomas Okken called FREE42. It is an excellent replica of the HP42S (no longer available). Free42 is available on PC/Android and other platforms. It’s a free (as in free beer) utility with great abilities. There are extensions to the HP42S as described on his web page.
Following up on that, I have been using a DM42 calculator from SwissMicros. It incorporates the above Free42 software. Whilst not the cheapest calc, it feels like a brick out-house and seems to work very, very well (34 decimal places too! using the Decimal executable.) The only slight drawback would be that it needs good lighting to view (and/but it does have different font sizes).
Just an off topic and I am in NO way affiliated to this.
Best regards