Microchip Direct have over 1000 PIC17C42A-25I/L in stock at ?7.21 each. The hgher speed should not be an issue.
?https://www.microchipdirect.com/product/search/all/PIC17C42A?facet=on&facet=true&fq={!tag=PT}PackageType_s:(%22PLCC%22)&facet.field=PackageType_s&start=0&rows=50